`PROJECT_ROOT_PATH is set, using /... as cwd for execution payload` is
printed to stdout during unittest discovery and execution, leaking into
the Test Results panel.

- Remove `print()` in `python_files/unittestadapter/execution.py`
(execution path)
- Remove `print()` in `python_files/unittestadapter/discovery.py`
(discovery path)

All functional logic (reading the env var, setting `top_level_dir`,
updating the global) is unchanged.

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Co-authored-by: copilot-swe-agent[bot] <[email protected]>
Co-authored-by: eleanorjboyd <[email protected]>